There are two primary goals in this project: a) to determine the capacity of patients with primary or metastatic cancer of the liver to metabolize drugs relative to values in normal adult volunteers; b) to determine how patients with primary or metastatic cancer of the liver respond to an inducer of hepatic microsomal drug metabolism such as phenobarbital. 1. In patients with documented hepatic metastases not receiving other medications and not exhibiting major fluctuations in hormonal, cardiovascular, hepatic or renal function, the following studies will be performed: a. Antipyrine will be administered at 9 a.m. and blood specimens will be drawn at noon, 3 p.m., 6 p.m., and 9 p.m. Plasma antipyrine concentrations will be measured spectrophotometrically and plasma antipyrine half-lives will be repeated three times at varying intervals, in an attempt to relate plasma antipyrine half-lives to the parameters of hepatic metastases and hepatic function. 2. Antipyrine half-lives in plasma will be obtained one week prior to and on the day after a three-day course of phenobarbital, as an index to the capacity of liver containing metastases to respond to an inducing agent. These studies have a direct application in the therapy of patients with liver metastases since dosages of drugs metabolized by hepatic microsomal enzymes might be altered, should the proposed investigation reveal that in the presence of liver tumors, antipyrine metabolism is significantly changed.